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Trek oversized front derailleur clamp

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Trek oversized front derailleur clamp

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Old 12-07-17, 12:41 PM
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guntherkern
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Trek oversized front derailleur clamp

Hi,

I am trying to get rid of the original derailleur on a Tek X-caliber bike.
These bikes use 36.2 mm downtubes. They are not 34.9mm!! I measured 3 times.
If anyone has an idea how to mount a fornt derailleur on tghis bike that can shift from 28 to 46 teeth on double front ring setup I would appreciated hearing about ideas.

Thanks,
Gunther
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Old 12-07-17, 12:57 PM
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maddog34
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e-mount... goes between the BB and frame...
https://www.ebay.com/itm/Shimano-Xtr...YAAOSwKUxZlb9w

there are several variants available... an older Altus or LX would probably be best for your rings.

friction or indexed shifters?
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Old 12-07-17, 01:19 PM
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These bikes use 36.2 mm downtubes.
Derailleurs mount on the seat tube, not the downtube ..



34.9 is 1 3/8" ... lots of tube standards, on bicycles, are sized in inches, and then stated in metric equivalents.


You get an adapter to a Brazed on Italian Type Fitting, style, which is the most common type sold these days..


http://www.mnwwg.org/docs/fraction_conversion_chart.pdf





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Old 12-07-17, 03:02 PM
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Originally Posted by jimc101 View Post
34.9 is the default/only size for Shimano MTB FD's, they use spacers to reduce, so sourcing will be no problem.
read the original post SLOWLY... let "36.2mm" soak in...
then realize the irrelevance of your post.
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Old 12-07-17, 05:56 PM
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Originally Posted by guntherkern View Post
Hi,

I am trying to get rid of the original derailleur on a Tek X-caliber bike.
These bikes use 36.2 mm downtubes. They are not 34.9mm!! I measured 3 times.
If anyone has an idea how to mount a fornt derailleur on tghis bike that can shift from 28 to 46 teeth on double front ring setup I would appreciated hearing about ideas.

Thanks,
Gunther
Do you know the year of your bike? I'd be surprised if it wasn't intended for a 34.9 clamp. Have you measured lower, close to the bb? It may taper for a low clamp. Otherwise e type.

Also 46/28 is not a supported gearing combination by any manufacturer. Try 44/28 which is semi commonly available. 44/11 is plenty.

Last edited by cpach; 12-07-17 at 06:03 PM.
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Old 12-07-17, 06:49 PM
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Sram XO front derailleur seems to come in the weird Scott specific oversized clamp: https://www.universalcycles.com/shop...s.php?id=37443

Lot of options there, but scroll down and they have a double specific one with the huge clamp. Could get one of those and shim it, the Scott style clamp is 38.2mm. Somewhere exists other braze on adapters and derailleurs in the 38.2 size if you look around, most seem to be carbon clamps that take a road derailleur.

I'd be inclined to just modify an existing 34.9 clamp or derailleur. Wouldn't take long to file, grind, dremel etc to make one fit.
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Old 12-07-17, 10:36 PM
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Thank you all for useful replies. Very much appreciated.
FYI the bike is a Trek X-caliber 2018 and all their X-caliber use an oversized seat tube that is actually 36.5 mm.
The gears come from an Italian e-bike kit called bikee bike. They use a 28 and 46 chain ring on a motor that mounts through the bottom bracket. They just are coming on the market and I am trying to get this kit work. It likely will work well on a a Trek Dual Sport 3 which has a triple crank with the respective shifter on the seat tube which is a clamp on and can be moved if needed.
Lesson learned: it is not easy to retrofit thos emotors in modern Tek MTBs.
I do like the option of a bottom bracket front derailleur mount but it needs to be hight adjustable I think.
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Old 12-07-17, 10:40 PM
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they don't use a clamp type front derailleur. there are a few posts on the seat tube down by the bottom bracket that the front derailleur will mount to. it's a new MTB specific standard.
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Old 12-08-17, 12:07 AM
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OK, I was guessing that a conversion project wouldn't be on a new model year bike. Seriously--why not just buy a bike built as an eBike? I found the bikee site confusing about chainring size. Very few mountain doubles have chainrings larger than 38t so even with a band clamp derailleur the shaping of the derailleur cage is going to suck with a 46t big ring. At that size it's better to use a road double derailleur and flat bar road shifter. Regardless nothing's going to work well on that X Cal, as it uses a low direct mount derailleur.

This is also the only mid drive system I've ever seen with multiple chainrings.
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Old 12-08-17, 12:31 AM
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Found this thing: https://www.pinkbike.com/buysell/1540128/

Apparently someone used to make a direct mount to road braze on clamp specifically for Trek/Gary Fisher frames. Seems they are out of business now though.
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